COMPOSITE BODIES AND THEIR MANUFACTURE

Abstract

The application describes methods of making composite bodies including fibre-reinforced composite material with carbon fibre reinforcement and also a metal-containing portion (4). The metal-containing portion (4) is formed by laying up metal reinforcement elements, such as tapes of titanium alloy, among the carbon fibre reinforcement tapes which make up the composite body. The proportion of metal reinforcement may increase progressively towards the surface and/or towards an edge (14) of the composite body. In an example, metal leading and trailing edges (14,15) of a fan blade (1) are integrally formed in this way.

Claims

1. A method of making a composite body comprising assembling a body form by laying up multiple overlapping lengths of reinforcement material comprising carbon fibre reinforcement material; providing curable polymeric material impregnating the laid-up reinforcement material, and curing the polymeric material to form a solid matrix, characterised by laying up lengths of metal reinforcement as a said reinforcement material at a predetermined region of the body form, to form a metal-containing portion of the composite body.

2. A method according to claim 1 in which the lengths of carbon fibre reinforcement material and metal reinforcement are laid up by automated fibre placement from a placement head.

3. A method according to claim 2 in which lengths of carbon fibre reinforcement material and metal reinforcement are laid up side by side from the same placement head.

4. A method according to claim 1 comprising bonding adjacent metal reinforcements to one another after the laying-up, by metal-to-metal bonding.

5. A method according to claim 4 in which adjacent metal reinforcements are bonded to one another by welding and/or by interlayer powder bonding.

6. A method according to claim 5 in which the metal reinforcements as laid up carry fusible metal powder for interlayer powder bonding.

7. A method according to claim 4 in which the curable polymeric material is impregnated into the assembled body form of reinforcement material after the metal-to-metal bonding of the metal reinforcement.

8. A method according to claim 1 in which at the metal-containing portion, the reinforcement material is laid up with the proportion of metal reinforcement relative to non-metal reinforcement increasing from a lower to a higher proportion.

9. A method according to claim 1 in which the metal-containing portion includes a full-metal portion where all of the reinforcement is metal.

10. A method according to claim 1 in which the metal-containing portion is at an exterior surface of the composite body.

11. A method according to claim 1 in which the composite body is a blade, vane, casing or housing.

12. A method according to claim 1 in which the composite body is a fan blade and the metal-containing portion thereof extends along an edge of the blade.

13. A composite body having a body form comprising multiple overlapping laid-up layers made from lengths of reinforcement material embedded in a cured polymeric matrix material, the body form comprising a metal-containing portion where the reinforcement material comprises both carbon fibre reinforcement and metal reinforcement.

14. A composite body according to claim 13 in which the metal-containing portion is at a surface of the composite body.

15. A composite body according to claim 13 in which the metal-containing portion is at an edge of the composite body.

16. A composite body according to claim 13 in which the proportion of metal reinforcement relative to carbon fibre reinforcement increases towards the exterior of the body form and/or towards an edge thereof.

17. A composite body according to claim 13 in which the metal reinforcement elements are fused to one another in the metal-containing portion, at least at a surface or exterior region thereof.

18. A composite body according to claim 13 which is a gas turbine engine component in the form of a plate, wall, band, tube, flange, blade, vane, housing or cylinder.

19. A composite body according to claim 18 which is a fan blade and the metal-containing portion extends along a leading and/or trailing edge thereof.

20. A gas turbine engine containing a component as specified in claim 18.

Description

[0036] The invention is now explained in more detail with reference to the accompanying drawing figures, in which

[0037] FIGS. 1 and 2 have already been described and show a conventional form of metal sheath used for edge protection on a fan blade, in face view pre-assembly and as a chordwise section after assembly;

[0038] FIG. 3 has already been described and shows a gas turbine engine in which components embodying the invention may be used;

[0039] FIG. 4 is a chordwise section showing a graded composition of reinforcement materials in a fan blade embodying the present invention;

[0040] FIG. 5 is a schematic fragmentary face view near the edge of the composite body form for the blade during assembly, showing reinforcement being laid up;

[0041] FIG. 6 is a schematic cross-section through a metal reinforcing tape;

[0042] FIG. 7 is a schematic cross-section through a metal reinforcing tape;

[0043] FIG. 8 is a schematic fragmentary chordwise sectional view near the edge of the composite body form, showing metal and carbon reinforcement tapes as laid up;

[0044] FIG. 9 is a schematic fragmentary chordwise sectional view corresponding to FIG. 8 showing a first mode of bonding the metal tapes, and

[0045] FIG. 10 is a schematic fragmentary chordwise sectional view corresponding to FIG. 8 showing a second mode of bonding the metal tapes.

[0046] FIG. 4 is a chordwise section of a compressor fan blade 1 embodying the composite body of the invention. According to the conventional form it has a suction face 11 and a compression face 12 constituting oppositely-directed main faces of the body 1, and a leading edge 14 and trailing edge 15 whose edge surfaces connect to the main faces 11, 12. Each of the leading edge 14 and trailing edge 15 comprises integrally a metal-containing edge portion 4,4′, the inwardly-directed boundary of which is indicated schematically by broken lines. The body form 1 has a main part 3 consisting of carbon fibre-reinforced plastics, e.g. epoxy resin, and this main part 3—which contains no metal—has leading and trailing projections 31,31′ extending inside the metal-containing portions 4,4′ which are U-shaped or channel-shaped in form, although integral with the body 1.

[0047] According to a generally known method the body form 1′ is assembled by laying up (superimposing) successive layers of elongate reinforcing materials 6. FIG. 5 shows this operation schematically near the leading edge 14. An AFP (automated fibre placement) head 21 is moved automatically over the surface of the body form 1′ to lay down a course 7 of multiple side-by-side elongate reinforcement elements 6. The AFP head 21 incorporates a resilient presser to press the set of reinforcements 6 down against the layer 77 below, and is supplied with lengths of reinforcement which can be selectively stopped, started or cut, or one material substituted for another, so that the course 7 may consist entirely of carbon fibre tape 66, of metal tape/foil 61 (e.g. of titanium or titanium alloy), or of a combination of metal and carbon tape simultaneously, at controlled proportion. The skilled person will be aware that carbon fibre tape and metal tape can be laid by alternative apparatus and methods, such as by winding and the like. Also the metal may be laid up in an operation distinct from the laying up of carbon, but the present proposal of simultaneous laying up of metal and carbon is preferred for efficiency and because it allows close integration of the materials and fine local adjustment of the proportion of one to the other.

[0048] In the illustrated embodiment the carbon fibre tape 66 is laid by a “dry fibre” method in which it is coated only with an adhesive binder 661 (see FIG. 7) to hold it in place on the adjacent composite layers 7,77. Again as well known, an alternative is to feed the carbon fibre as pre-impregnated tapes or tows carrying the curable polymer which will form the matrix of the composite body.

[0049] The metal tape is desirably fed in a form adapted for subsequent metal-to-metal bonding, e.g. as shown in FIG. 6 which shows schematically the metal tape 61 e.g. of titanium or titanium alloy, carrying on its surfaces a layer of fusible metal particles 8. These are of a suitable composition to promote metal to metal joining. They may for example be of the same composition as the tape e.g. titanium or titanium alloy. An adhesive binder layer 611 holds the fusible metal particles 8 in place and may additionally help to bind the dry reinforcement assembly together as the body 1′ is laid up. Tape of Ti or Ti 6-4 for example is readily available.

[0050] In accordance with present proposals, the metal reinforcements 61 are introduced into the lay-up towards the leading and trailing edge regions 14,15, in increasing proportion towards the surface thereof and in increasing proportion towards the edge thereof (relative to the main body 3) so as to create the metal-containing portion or metal edge portion 4,4′ in each case. Thus, the metal-containing edge portion 4 begins at a low-metal region 41 where e.g. about one third of the laid-up reinforcements are metal, through an intermediate-metal region 42 where e.g. about two thirds of the reinforcements are metal, to an all-metal region 43 at the edge tip where all of the reinforcements are metal reinforcements 61 so that—especially when dry fibre placement is being used—the material consists essentially of side-by side metal tapes adhered to corresponding metal tapes beneath. Of course the tapes of different layers are differently oriented, as is well known.

[0051] In practice such a body form usually contains some hundreds of layers, with the overlying carbon and metal tapes running in different directions, so the cross-sectional fragmentary view shown in FIG. 8 is highly schematic and simplified. It shows schematically (and in fragmentary longitudinal sections) four regions progressively further from the edge. At the edge region on the right of the figure, all of the tapes are metal tapes 61. The metal percentage among the reinforcing tapes is indicated by the % value beneath each fragmentary section. Further towards the left of the figure, into the main body of the blade, the metal tapes 61 are interspersed among carbon tapes 66 at progressively decreasing proportions: at the first inward region at 66% metal 61′ to one-third carbon 66, at the next region 33% metal 61″ to two-thirds carbon 66′ and at the fourth region entirely carbon tape 66″.

[0052] At this stage various procedures are possible to accommodate metal-to-metal bonding of the metal tapes 61. Where the carbon elements (at least) are pre-impregnated with curable polymer, or following an impregnation stage with curable polymer which avoids impregnating the edge region, the matrix may be cured to consolidate the composite element, leaving the metallic tapes 61 generally un-joined because to the extent that are not encapsulated in polymer. By applying local heating to the metal-containing region 4 the interlayer powder particles 8 can be fused to form a direct joint—effectively brazed—between the metal tapes 61 of adjacent layers.

[0053] Any suitable heating method may be used, such as induction heating, resistance heating or direct heat. A possible disadvantage of this method, depending on the conditions required for metal-to-metal joining, is that the metal bonding conditions may adversely affect the matrix resin nearby. However, it is possible to reduce this adverse effect by directing the metal heating only to regions not impregnated with polymer composite, so that while some metal layers must then rely on the composite polymer to hold them in place (i.e. without metal-to-metal bonding) the all-metal regions towards the edge can still be fusion-bonded. FIGS. 9 and 10 show these alternatives,

[0054] FIG. 9 shows all available metal-to-metal bonding done by welding, so that at the edge region the metal piece is fully integrated, at the next region only partially while by the third region metal tapes are separated by carbon tapes. FIG. 10 shows metal-to-metal bonding done only at an all-metal region localised near the edge, with some adjacent metal tapes 61 further from the edge being joined only via the polymer matrix.

[0055] In a more preferred procedure, metal-to-metal bonding of the metal tapes 61, e.g. by fusion bonding such as powder interlayer bonding as described, is done in the absence of the curable matrix polymer. This can be achieved by assembling the composite body 1′ under “dry fibre placement” conditions, i.e. using only a stabilising binder 661 on the carbon fibre tapes 66. The body having been assembled with the requisite distribution of metal reinforcements at the metal-containing portions, these portions can then be subjected to conditions to effect the metal-to-metal bonding, such as by powder interlayer fusion. Subsequently, liquid polymer matrix resin can be infiltrated into the fibrous permeable body lay-up—this is known—and then cured. In this way the matrix resin is not exposed to the high temperature conditions normally required for metal-to-metal bonding. The same structural and bonding options as in FIGS. 8 to 10 are still available.

[0056] The skilled person will appreciate that the mode and extent of metal-to-metal bonding can be chosen in dependence of the form of the component and the performance requirements on the resulting metal-containing portion. In some cases regions of the metal reinforcement may be joined only by adhesive means e.g. by matrix polymer or by separate binder, with other portions e.g. at the surface being metal-to-metal bonded for example by welding, such as by resistance welding, laser welding or friction stir welding, to connect the metal elements to one another and close the surface.

[0057] If necessary the exposed metal surface can then be finished by other means. In the example herein of a fan blade, it may be ready for use. In other situations the metal part may have to undergo further processing for connection to another part, such as a metal part.